Phase indicating means



. y 7, 1940- c. c. SHUTT 2.200.103

PHASE INDICATING MEANS Filed April 21. 19:58

' Fly] wo'raemsar Paaoucms PEA/c 30 mugg- 3 I INVENTOR Char/e5 C 5/2u77fATTORNEY Patented May 7, 1940 UNITED STATES- PATENT OFFICE PHASEINDICATING MEANS vania Application April 21, 1938, Serial No. 203,807

4 Claim.

This invention relates to measuring and indicating systems, andparticularly to a system for measuring and indicating'the angulardisplacement of the rotor of a synchronous machine under load withreference to its no-load position.

One object of the invention is to provide a simple system including asimple device for measuring the angle of displacement of the rotor of asynchronous machine under load and while it is operating.

Another object of the invention is to provide a system for measuring theangular displacement of the rotor of a synchronous machine under load,and for indicating or utilizing such meas- 10 urement as a means ofcontrol for the system in which the synchronous machine is connected.

When a synchronous motor is operated under load. the rotor becomesslightly retarded or angularly displaced from its normal mechanicalphase position, which it would occupy normally under no load conditionswhen the mechanical in-phase condition would correspond exactly with theelectrical in-phase condition.

, Under load, however, the rotor tends to be displaced slightly sincethe magnetic locking connection, which is the magnetic flux between thestator windings and the rotor windings, may be regarded as having adegree of resiliency within the limits which'hold the machine locked instep although operating under such load.

In the same way, the rotor of a synchronous generator when operatedunder load is moved slightly in advance of the normal mechanical phaseposition it would occupy at no load condition.

' In'order to measure the angular displacement of the rotor, whether ofa motor or of a generator, under load conditions, I provide, forexample, a small auxiliary generator device mount- 0 ed either on thesame shaft with the main rotor,

or suitably geared to the shaft of the main rotor, in order to derive achecking voltage having the same frequency as that'of the synchronousmachine.

The voltage derived from the auxiliary generator is supplied to apeaking transformer, from the secondary of which a sharp peak voltage ofvery short duration may be obtained. A similar peaking transformer isenergized from one of the stator windings of the synchronous machine. Ineach .case the maximum voltage derived from the secondary windings ofeach of the peaking transformers, namely, the tip of its peaks, willhave a given phase relation to the point of maxis mum-voltage suppliedto the primary windings conductive.

of the transformer. Each peak voltage may therefore be utilized toindicate the time when the voltage across the primary winding of thetransformer is at its point.

Byproperly combining the two peak voltages, g I may procure a controlvoltage wherethe two peak voltages are in phase which is sufflcient inmagnitude and phase position to be utilized to control the potential ofthe grid element of a three-element electronic tube to render the tube10 The tube, when thus made conductive, transmits an operating impulseto energize an indicating device or to operate a control device. Properoperation of the tube is effected by establishing an initial bias whichmust 1 7 the angular displacement that may be necessary to bring thepeak voltage from the auxiliary source into phase with the peak voltagefrom the 25 main synchronous machine. To permit such measurement to bemade while the main rotor is rotating, the auxiliary generator isprovided with an adjustable angularly movable stator, suitably mountedin a stationary cradle, to per- 30 mit the stator to be rotatablyadjusted through an angle until the two peak voltages can besynchronized to operate the three element control tube. The amount ofangular rotation or adjustment of the auxiliary stator then deter- 5mines the angular displacement of the rotor of the synchronousmachine.

The manner in which the various elements of the system are arranged tooperate in accordance with the principle of this invention isillustrated in the accompanying drawing, in which: a

Figure 1 is a diagram of the circuit arrangement' of the variouselements,

Fig. 2 is a graph showing the usual relationship between the peakvoltage and the primary voltage of the synchronous machine,

Fig. 3 is a graph showing the usual relationship. of the primary voltageand of the peak voltage of the auxiliary generator,

Fig. 4 is a side view of a modification of an 50 auxiliary generator forestablishing peak voltages,

, Fig. 5 is an end view of the auxiliary generator shown in Fig. 4, and

Fig, 6 is a front view of another form of auxiliary generator.

As shown in Fig. 1, a synchronous machine 13, such as a synchronousmotor or a synchronous generator, is provided with a stator H and arotor l2. The rotor I2 is mounted upon a shaft II which serves also tosupport a rotor ll of an auxiliary testing synchronous generator II thatis also provided with a stator I 6. The stator I of the auxiliarygenerator is adjustably supported in two stationary cradle. elements l1and". The stator l6 may be rotated by suitable adjusting means to anydesired position within a predetermined testing angle that is sufficientfor this purpose. The adjusting means may comprise a worm and gearmechanism provided with an operating handwheel 20. The stator frame issuitably marked with an index Is to indicate a zero or neutral position,and is marked with graduations 2| and 22 to indicate up to 90 generatorand up to 90 motor positions, respectively. A stationary finger 23,adjacent the stator, is provided to indicate the normal neutral positionof the stator IS. The rotor of the auxiliary generator I5 is providedwith suitable field magnet windings 24, and is also provided with thesame number of poles as are found on the rotor ii of the mainsynchronous machine H). For simplicity, the auxiliary rotor 14 and themain rotor l2 are shown with two poles. The auxiliary generator shouldhave the same number of poles on both rotor and stator, as the maingenerator or motor, when the auxiliary generator is direct-connected.More generally, whether the auxiliary generator is direct-connected ornot, it must generate a voltage of the same frequency as the mainmachine.

The auxiliary generator in Fig. 1 is shown with three phase windings,corresponding to those of the main machine, merely for illustrativepuras phase 21, and the primary winding of a second peaking transformer3| is connected across a winding 21' of the stator l6 of the'auxiliarygenerator l5 which corresponds to the winding 21. The secondary windingof main peaking transformer is connected to a potentiometer resistor 33,and the secondary winding of auxiliary peaking transformer 3| isconnected to a potentiometer resistor 32. The two resistors 32 and 33are connected through a conductor 34 in such-direction as to add thevoltages across them. The free terminal of the potentiometer resistor 32is connected through a biasing battery 35 to the grid element of a threeelement thermionic tube 33. The free element of the resistor 33 isconnected to the cathode of the thermionic tube 33 through a connectionincluding the secondary winding of a heating transformer 31 for thefilamentary cathode of the tube. The three element tube is connected toan external circuit through two conductors 38 and 39 to permit a controlcurrent to be transmitted by the tube for indicating purposes or forcontrol purposes.

When the stator winding 21 of the main machine ||l is energized, themain "peaking transformer 30 will be energized to provide the main peakvoltage AI, shown in Fig. 2. The voltage across the primary is indicatedby the curve A.

The primary voltage on transformer 3| is indicated by the curve B, andthe peak voltage of the secondary of transformer 3| is indicated by thecurve Bl in Fig. 3.

The load on the auxiliary generator I5 is constant and relatively small,being only the current required by the transformer 3|. With machine IDunloaded the zero point on the scale I9 on the stator l6 should be setso that it coincides with the pointer 23 when the voltage impulse fromthe peaking transformer 3| is in time phase with an impulse of likepolarity from the secondary of transformer 30. If the main machine, as amotor or as a generator, is to be connected to a large system, suchphase check should be made when the machine is substantially unloadedand when the terminals of the main machine are energizedand connected tothe system. If the main machine is to operate as an isolated generator,such polarity check should be made with the generator excited andunloaded. After the setting is made; and the pointer is at zero, thetime phase of the voltage generated in the Winding of the auxiliarygenerator will be proportional to the displacement of the rotor of themain machine from its no-load position. When the main machine is underload, the rotor is mechanically angularly displaced with respect to itsnormal neutral unloaded position. The voltage curve B will becorrespondingly displaced and the peak voltage Bi will also consequentlybe correspondingly displaced.

While the machine is operating, the peak voltage Bl may be shifted byangularly adjusting the stator Hi to change the phase position of themain voltage B. When the peak voltage BI is shifted to in phase relationwith the peak voltage Al of the main machine, the two peak voltages AIand BI will add to establish a voltage of sufficient value to overcomethe biasing voltage 35 on the grid of the tube'36, and the resultant ofthe peak voltages will thereupon energize the grid sufficiently torender the tube conductive. The tube 36 will thereupon transmit anenergy impulse which may be utilized to energize an indicating device asa lamp 40, or to energize a control device to effect any desiredexternal operation.

Instead of the combination of the auxiliary generator of the type shownin Fig. 1 with a peaking transformer, a modified form of peak voltagegenerator may be employed as shown in Figs. 4, 5 and 6;

In Fig, 4 is illustrated an electromagnetic device comprising astationary core 5| supporting a primary winding 52 and a secondarywinding 53. An armature 54 to complete the magnetic circuit of the core5|, to enable the core to function as a transformer with the twowindings 52 and 53, is mounted on the main shaft in any suitable mannerto rotate with the shaft. The core is mounted on a support adjacent theshaft so that the armature will move past the core closely enough tocomplete the magnetic circuit of the core. The primary winding 52 isenergized by direct current, and as the armature quickly completes themagnetic circuit of the core once ,each rotation of the shaft, thesecondary winding is energized to induce a sharp peak voltage of shortduration. This peak voltage will always .be in definite fixedrelationship to the shaft. By making the support for the core 5| or forthe armature 54 angularly adjustable as in Fig. 5, the core may be movedangularly around the shaft until the peak voltage is synchronized withthe peak voltage derived from the synchronous machine winding.

In order to establish optimum initial conditions, the armature bar 54should be secured on the shaft in line with the center line of a rotorpole on the shaft. Fig. 5 shows an end view of the impulse generator andillustrates the arcuate support 55 for angularly adjusting the core 5|so that the peak voltage induced therein may be shifted to synchronizewith that derived from the synchronous machine. By making the angularspm of the bar mounted on the shaft short enough, the voltage wave maybe made sharp enough to eliminate transformer M.

In Fig. 6 is shown a further modification of an auxiliary voltagegenerator. The core 8! supports primary winding 62 and secondary winding63, and is itself provided with pole tips 64 and 65. A disc 66 ismounted on the shaft'and disposed to pass between the pole tips 64 and86. One or more steel pins 61 are mounted on the disc to substantiallyclose the magnetic circuit between the pole tips 84 and 65. When morethan one pin is used, the pins should be equally spaced and should beequal to half the number of poles in the main machine so the auxiliarypeak impulses I can be synchronized with the main pulses of one selectedpolarity.

My invention is not limited to the specific arpeak imrangement, or tothe details shown since they may be modified without departing fromthespirit and scope of the invention as set forth in the appendedclaims.

I claim as my invention:

1. A testing system for measuring the angular displacement of the rotorof a synchronous machine under load, comprising means connected to awinding of the stator to establish a voltage wave of sharp peak form andshort duration, means driven by the rotor shaft to establish anauxiliary voltage wave of sharp peak form and short duration similar tothe other voltage wave, a circuit for both voltage waves, manuallyoperable means for varying the phase relationship between the twovoltages, means for detecting synchronism between them, and means formeasuring the angle necessary to establish synchro- 2. A tating systemfor measuring the angular displacement of the rotor of a synchronousmachine under load, comprising transformer means connected to andenergized from a winding of the stator of the synchronous machine anddesigned to produce a voltage of peak wave form and of short effectiveduration, an auxiliary generator rotor driven by the main rotor, arotatably adjustable stator for the auxiliary generator, transformermeans connected to and energized from the auxiliary generator anddesigned to produce a voltage of the same frequency as themain voltageand having a peak wave form of short effective duration, means combiningthe two voltages in an electric circuit to detect sync'hronism betweenthe two voltages, and means associated with the adjustable stator of theauxiliary generator for indicating the amount of angular movement of thestator necessary to place the peak voltages in phase, thereby toindicate the angular displacement of the main rotor shaft under loadconditions.

3. A system for measuring the angular displacement of the rotor of asynchronous machine, comprising means for deriving a substantiallypeaked test voltage in synchronism with the voltage on a stationarywinding of the machine, means for simultaneously generating a secondsubstantially peaked voltage which varies in accordance with themechanical, displacement of the shaft, and means for measuring theelectrical angle between the two voltages.

4. A system' for measuring the angle of displacement of a rotor of asynchronous machine I having a stator winding and a shaft for the rotor,comprising a transformer connected to the stator winding, a transformercontrolled by the shaft, phase control means for the shaft controlledtransformer, means for indicating syn chronism as established by thephase control means between the two voltages derived from thetransformers, and means associated with the phase-control means forindicating the electrical angle of adjustment necessary to bring the twovoltages into phase.

CHAS. C. SHU'I'I'.

